In the daily preparation of military aircraft, it is often necessary to store regularly updated security codes, known as crypto-variables or keys into weapon control and other communication systems such as friend or foe identification systems (IFF). This task is currently performed by a portable code storage box which is connected to an aircraft code memory device by means of conventional pin connectors. In the naval fleet this transfer of security codes to an aircraft is done during pre-dawn hours in all types of weather and sea conditions. On an aircraft carrier, this is manually performed by a cryptocustodian to aircraft that rests on the flight and hanger decks.
Although the procedure is generally satisfactory, it is a time-consuming one requiring proper connector hook-up between aircraft and the custodian's portable security code box. Due to the harsh environment, connectors often deteriorate and the reliability of the connectors is limited. Typically, such connectors are called upon to transfer digital security codes to an internal code memory of the aircraft. When the connectors between the portable code box and the aircraft evidence physical or electrical deterioration, errors in code transfer are possible.
In my co-pending patent application Ser. No. 224,605, filed July 27, 1988, a coupling device was disclosed which preferably magnetically transfers data and circuit power to an aircraft security code storage circuit without the inclusion of mechanical pin connectors. In the environment of an aircraft, the conventional custodian's security code portable transfer box is equipped with a sending unit which is magnetically attached to the exterior of an aircraft skin. At an aligned position along the interior surface of the skin is a receiving pick-up unit which magnetically picks up the digital code and low voltage power being transferred by the sending unit. The sending unit is easily removed after signal and power transfer have taken place by simply detaching it from the aircraft. As will be appreciated, such a simple and elegant technique avoids the problems of pin-type connectors which have been employed heretofore.
In actual utilization of the coupler described, it is impossible to completely eliminate electromagnetic radiation which might be detected by a nearby intruder, such as an enemy submarine. Accordingly, it would be highly desirable if the coupled data could be encrypted in a manner that would avoid useful decoding of the coupled data.